算法第二周作业

2.1

import java.util.*;
public class suanfa {
//输入：一个长整数，若为素数则返回 true,否则返回false;
public static int isPrime(long a) {
int b=1;
for(int i=2;i<Math.sqrt(a);i++){
if(a%i==0)
b = 0;
}
if (a==1) b=0;
return b;
}
public static void main(String args[]){
System.out.println("请输入一个长整数:");
Scanner scan=new Scanner(System.in);
long a = scan.nextLong();
int b =isPrime(a);
if(b==0){
System.out.println(a + "非质数 所以返回 " + b);
}else{
System.out.println(a + "为质数 所以返回" + b);
}
}
}

2.2
import java.util.Random;
import java.util.Scanner;

public class createRndInteger{
public static void main(String[] args) {
System.out.print("请输入随机生成n bit位的长整数的长度n：");
Scanner scanner=new Scanner(System.in);
int x= scanner.nextInt();
long random= createRndInteger(x);
System.out.println("随机生成的" + x + "位长整数是：" + random);
}
public static long createRndInteger(int x){
StringBuilder s=new StringBuilder();
for(int i=1;i<x+1;i++)
{
int num=(int)(Math.random()*2);
s.append(String.valueOf(num));
}
long a=Long.parseLong(s.toString());
return a;
}
}